In the dental field it is now well recognized that the alloy to which low-fusing porcelain can be successfully applied so as to have complete adhesion must be compatible from the standpoint of coefficient of linear expansion and contraction at the fusing temperature of the porcelain; and that such alloy must provide on its surface oxides which facilitate the adhesion of the porcelain. Furthermore, the oxides have to be an integral part of the alloy, so that such oxides cannot be lifted from the alloy by the fluxing effect during the application of opaque porcelain to the alloy.
It is also well understood that after application of the porcelain to the alloy, the porcelain surface should not check, crack or separate from the base alloy.
There are on the market today various opaque porcelains which are especially prepared and sold for application to dental alloys. The opaqueing materials of such opaque porcelains vary from one to the other and the basic ingredients of such opaque porcelains are not fully disclosed in any literature with which I am familiar.
Among the various opaqueing porcelains with which I am familiar is one offered for sale and sold by Dentsply International Inc. of York, Pennsylvania under the trademark BIOBOND. Another is offered and sold by Vita Zahnfabrik H. Rauter K.G., of Sackingen, Germany, under the trademark VITA.
I also know that there are other opaque porcelains sold under the trademark CERAMCO by Ceramco, Inc. of Long Island City, New York and under the trademark HOWMEDICA by Howmedica, Inc. of New York, New York.
Essentially all of these opaque porcelains for dental application are said to be low fusing in that they will fuse at a temperature of about 1800.degree. F. to dental alloys and will adhere to the same provided all other conditions are met for fusing such porcelains to the metal alloy.